Currently, an LED tube may either be plugged into the AC electric power supply or a power supply system having an inductance ballast. The LED tube is not adapted to the AC electric power supply, the power supply system having an inductance ballast, and the power supply system having an electrical ballast. Therefore, a fluorescent lamp/tube used in the power supply system having the electrical ballast may not be directly replaced with an LED tube when the fluorescent lamp/tube is burned. Moreover, when an LED tube is applied to the power supply system having the inductance ballast, and when the inductance ballast malfunctions, the LED tube also fails to work properly because the failed inductance ballast may block the AC electric power supply from the LED tube. Accordingly, there is a need to provide an LED driver adapted to the AC electric power supply, the power supply system having an inductance ballast, and the power supply system having an electrical ballast.